PSLE The pupils at a school choir are divided in Group A and Group B. The ratio of the number of boys to girls in Group A is 7 : 3. The ratio of the number of boys to girls in Group B is 8 : 7. There are 3 times as many pupils in Group B as in Group A. There are 99 more boys in Group B than Group A. What is the total number of girls?
Group A |
Group B |
10 u |
15x2 = 30 u |
Boys |
Girls |
Boys |
Girls |
7 u |
3 u |
8x2 = 16 u |
7x2 = 14 u
|
Total number of pupils in Group A
= 7 u + 3 u
= 10 u
Total number of pupils in Group B
= 3 x 10 u
= 30 u
The total number of pupils in Group B is repeated.
Use LCM to make the total number of pupils in Group B the same.
LCM of 30 and 15 is 30.
Number of more boys in Group B than Group A
= 16 u - 7 u
= 9 u
9 u = 99
1 u = 99 ÷ 9 = 11
Total number of girls
= 3 u + 14 u
= 17 u
= 17 x 11
= 187
Answer(s): 187